Stabilized organic compositions



United States Patent 2,770,535 STABILIZED ()RGANIC COMPOSITIONS Eugene F. Hill, Birmingham, and David 0. De Pree, Royal Oak, Mich assiguors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 11, 1952, Serial No. 325,453

3 Claims. (Cl. 4469) This invention relates to the stabilization of hydrocarbon fuels containing organolead antiknock compounds.

, Our invention also relates to the inhibition of attack by oxygen of the antiknock material itself.

Hydrocarbon fuels under present requirements of highcompression engines are almost universally treated with antiknock compounds, the principal ingredient of which is tetraethyllead.

Both automotive and aircraft fuels are commonly blended with tetraethyllead before use. Such blending imposes a point of instability in the finished fuel, since the tetraethyllead is susceptible to some deterioration by contact with oxygen during the blending, storage and handling operations, with consequent formation of haze, loss of some antiknock value, and lessened performance in the engine. This point of attack is often overlooked in certain automotive fuels, as the base stock is often unstable itself. If, however, a stabilizing ingredient were added which is capable of protecting only the fuel, the attack upon the tetraethyllead would then become apparent. In aircraft fuels the reverse is true, that is the protection must center upon the antiknock additive, as the fuel itself is relatively stable. Furthermore, this phase of the problem becomes relatively more important in aircraft fuels, since the tetraethyllead content of such fuels is generally several times that present in automotive fuels.

Heretofore, it has not been possible to protect such fuels for internal combustion engines effectively by means of a single substance against the two above-described separate but related deleterious effects of contact with oxygen during the refining, manufacturing, blending, storage and handling operations. Furthermore, because of the specifications imposed on fuels by the rigid requirements of present day engines, particularly aircraft engines, it is essential that any material capable of protecting such fuels against deteriortaion must be elfective in extremely small quantities, on the order of one pound of additive per five thousand gallons of fuel, so that secondary problems do not arise through their use.

It is, therefore, an object of our invention to provide means for protecting such antiknock compounds against deterioration in the presence of oxygen. Another object of our invention is to provide means for stabilizing leadcontaining hydrocarbon fuels for internal combustion spark engines during the manufacturing, handling and storage of such fuels prior to their use. It is also an object of our invention to provide fuels containing tetraethyllead in which there is essentially no loss in performance characteristics clue to such deterioration of the tetraethyllead during blending, storage and handling. Still further objects of our invention will appear from thedescription of our invention as hereinafter disclosed.

The above and other objects can be accomplished by practicing our invention which comprises adding to organolead antiknock agents or materials containing organolead antiknock agents a small proportion of a substance derived from the class of hydroxyand aminosubstituted phenyl ureas and thio ureas.

In general, the organolead stabilizers of the present invention can be defined as those compounds containing the grouping wherein R1 is alkyl, cycloalkyl, aryl, or an aryl group substituted on the ring with a hydroxy, amino or alkylamino radical; R2 is hydroxyphenyl or aminophenyl, that is, an aryl group substituted on the ring with a hydroxy, amino or alkylamino radical; R3 is hydrogen, alkyl or aryl, and X is the oxygen or sulfur atom. Whenever in the further description of our invention hereinafter we refer to the term alkyl it is to be understood that we include both straight and branched chain saturated hydrocarbon radicals. As examples of straight chain satuarted hydrocarbon radicals we include methyl, ethyl, n-propyl, n-hexyl, and n-octadecyl. Such radicals as isopropyl, isobutyl, sec-butyl, isoamyl, and Z-methylhexyl serve as illustrative examples of branched chain saturated hydrocarbon radicals. By cycloalkyl radicals is intended such homocyclic radicals as, for example, cyclohexyl, methylcyclohexyl, fi-cyclohexylethyl, and the like.

To further illustrate the nature of these protective substances, the generalized formula X s l is presented to depict the substituted ureas and thio ureas comprising the organolead stabilizers of the instant invention. In this formula X stands for the oxygen or sulfur atom, R3 and R4 represent hydrogen or organic radicals further defined hereinafter, and A refers to the activating groups described hereinafter. In this generalized formula the numbers inserted in the phenyl radical are for the purpose of naming specific embodiments of our invention hereinafter. We have found that such compounds of our invention, wherein the activating group A of the phenyl radical is in the ortho or para position with respect to the N-nitrogen atom exhibit the greatest effectiveness, and are, therefore, preferred, although some activity is shown by the meta derivatives. The principal function of the groups R1, R3 and R4 is believed to be to impart the proper balance of the properties of solubility, misoibility, and compatibility to the stabilizer with the organolead compound or materials containing organolead compound which are to be protected. While the principal effect of these groups is as stated above, R can be further chosen to intensify the action of the principal antioxidant forming groups, and in particular this intensifying action is obtained by choosing R as a phenyl group substituted with one of the components A. In general, the phenyl substituent, A, which we refer to as an activating group, comprises amino and hydroxy radicals and hydrocarbon derivatives thereof. Thus, We can illustrate the group A byhydroxy, amino,N-methylamino, N,N--dimethylamino, N,N-diethylamino, N,N-methylethylamino, N,N-ethylbutylamino, N,N-diisopropylamino, N-dodecylamino, N-cyclohexylamino, N,N-cyclohexylmethylamino, etc. Thus, examples of the hydroxyphenyl and aminophenyl groups of our invention which impart the distinctive antioxidant activity to our stabilizing compounds include p-hydroxyphenyl, o-hydroxyphenyl, m-hydroxyphenyl, 3 methyl 4 hydroxyphenyl, 2-pentadecyl-4-hydroxyphenyl, p-aminophenyl, p-n-butyl aminophenyl, pdimethylaminophenyl, p-cyclohexylaminophenyl, p-methylethylaminophenyl and p-diethylaminophenyl.

Those substituents, R1, R3, and R4 which are chosen primarily to impart superior solubility properties to the stabilizers of our invention include alkyl, cycloalkyl, aryl, aralkyl, and alkaryl groups and substituted derivatives thereof. For example, we have obtained good solubility characteristics and maintained the high antioxidant effectiveness of the stabilizers of our invention by various combinations of hydrogen, o-chlorophenyl, phenyl, naphthyl, tolyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, amyl, pentadecyl, n-octadecyl, cyclohexyl, propylcyclohexyl, 'y-cyclohexylpropyl, benzyl, p-ethoxyphenyl, pmethoxyphenyl, and fi-hydroxyethyl groups on the N- and N-nitrogen atoms or on the substituted phenyl radical characteristic of the stabilizers of our invention.

While we do not intend that our invention be limited by the choice of the groups R1, R3 and R4, in the preferred embodiments of our invention these groups do not contain excessive amounts of certain atoms and radicals capable of off-setting the activating influence of the substituted phenyl radicals. For example, excessive amounts of halogen atoms or nitro groups are not preferred, although minor amounts can be tolerated.

The stabilizers of our invention may be further defined by reference to the following methods of preparation, which, while not restricting the scope of the varia tions possible in different embodiments of our invention, are representative of methods we have employed in preparing the specific materials described herein.

METHOD I Unsymmetrieal disubstituted ureas and thio ureas comprising the organolead stabilizers of this invention have been prepared by reaction between substituted phenyl or alkyl isocyanates or isothiocyanates, and substituted anilines or alkylamines, one combination of which is represented by the equation METHOD II Symmetrical thio ureas containing two of the characteristic activating groups of the stabilizers of the present invention have been prepared by heating carbon disulfide and substituted anilines in the presence of elemental sulfur according to the equation A A A By this method we have prepared the following examples of the compounds of our invention: N,N-bis(p-hydroxyphenyl) thio urea and N,N-bis(p-dimethylaminophenyl)- thio urea.

METHOD III Certain symmetrical disubstituted ureas comprising the organolead stabilizers of our invention are prepared by warming an aqueous solution of the appropriate aniline hydrochloride with urea. This method is illustrated by the manufacture of N,N-bis(p-hydroxyphenyl)urea.

METHOD IV We have prepared certain N-alkylaminophenylureas comprising our protective agents for organolead materials by hydrogen reduction of nitroaromatic ureas in the presence of an aldehyde ammonia, the method of reductive alkylation, according to the equation where R is an alkyl group. By this method we have prepared N- (p-hydroxyphenyl) -N- (p-n-butylaminophenyl urea, and N- (p-hydroxyphenyl) -N'- (p-isobutylaminophenyl) urea.

METHOD V Symmetrical disubstituted ureas comprising the stabilizers of the instant invention can be prepared by treating an aniline with phosgene, according to the equation A A A As an example of this method we have prepared N,N- bis(p-hydroxyphenyl)urea thereby.

The absorption of oxygen was measured directly by the standard method of the American Society of Testing Materials for determination of the oxidation stability of gasoline (Induction Period Method), ASTM designation: D525-46, as fully described in Part IIIA, ASTM Standards for 1946. According to this method the induction period is the period during which there is no absorption of oxygen by the test material as indicated by a drop in pressure, when placed in a testing bomb maintained at a temperature of C. with an initial pressure of 100 pounds per square inch gauge of oxygen. The Induction Period Increase (IPI) is the increase in the duration of this period caused by the addition of a. protective substance, and is a direct measure of the protection afiorded by such additive. Thus, the longer the IPI the more effective is the stabilizer. On the contrary, certain substances exert a pro-oxidant effect in which a negative IPI is obtained, that is, the duration of the induction period, or period of no absorption of oxygen, is less than in the absence of the additive.

To illustrate the protection afforded to hydrocarbon solutions of tetraethyllead by the stabilizers of our invention, we conducted a series of tests in which hot-acid isooctane, a paraffinic fuel which was carefully distilled from glass equipment and which contained 4.6 milliliters of tetraethyllead per gallon, was heated at a temperature of 100 C. in a stainless steel bomb with oxygen added to an initial pressure of 100 pounds per square inch gauge. Under these conditions the pressure in a bomb containing only isooctane and a tetraethyllead antiknock mixture underwent a sharp drop after four hours, indicating absorption of oxygen by the fuel mixture. The minimum concentration of each of several additives required to prevent a drop in pressure in a bomb during a period of sixteen hours at a temperature of 100 C. was thereupon determined. Thus, the efiective concentration shown in Table I is the quantity of additive required, ex-

pressed as milligrams per 100 milliliters of fuel, to afford a greater than 4-fold increase in the stability of the fuel.

cone, mg./ 100 ml.

N-(p-hydroxyphenyl)-N-phenylurea N-Phenyl-N-(p-hydroxyphenyl)thiourea N-n-Butyl-p-arninophenol sym -Diphenylurea Ethylenethiourea By reference to Table I the low effective concentration to produce a more than 4-fold increase in the stability of the fuel of the stabilizers of the instant invention is immediately apparent. Comparing Nos. 1 and 2, repre sentative of the deterioration inhibitor of our invention with No. 3, a commercial material widely used to stabilize gasolines, our compounds are from three and onehalf to seven and one-half as times as effective. By further comparing Nos. 1 and 2 with Nos. 4 and 5, the effectiveness of the activating groups characteristic of the stabilizers of our invention is further illustrated. Compounds 4 and 5 failed to protect the fuel mixture when added in amounts of six to eleven times the effective concentrations of representative organolead stabilizers of our invention.

Similar results are obtained when other stabilizers of this invention are employed to inhibit attack by oxygen or ozone of hydrocarbon fuels containing organolead antiknock compounds, such as, for example, tetraethyllead. Thus, when we employ hydroxyphenyl ureas, hydroxyphenyl thioureas, and the aminophenyland alkylaminophenyl ureas and thioureas comprising our stabilizers of both organolead antiknock additives and organolead-containing internal combustion engine fuel normally tending to deteriorate in the presence of oxygen at concentrations in the range between about 0.1 and l milligram per 100 milliliters of fuel effective protection is obtained. For example, when we employ N-benzyl-N-phydroxyphenylurea; N-n-propyl-N'-p-hydroxyphenylurea; N phenyl N p hydroxyphenylurea; N-phenyl-N-(3- methyl 4 hydroxyphenyl) urea; N-phenyl-N-o-hydroxyphenylurea; N-o-chlorophenyl-N-p-hydroxyphenylurea; N-p-tolyl-N-p-hydroxyphenylurea; N-phenyl-N-nbutyl N p hydroxyphenylurea; N-phenyl-N-m-hydroxyphenylurea; N-n-octadecyl-N-p-hydroxyphenylurea; N-phenyl-N-(2-pentadecyl-4-hydroxyphenyl)-urea; N-B- naphthyl-N-p-hydroxyphenylurea; N phenyl-N'-n-octadecyl-N-p-hydroxyphenylurea; N,N diphenyl N phydroxyphenylurea; N phenyl N-phydroxyphenylthiourea; N-o-tolyl-N-(2-methyl-4-hydroxyphenyl)-thiourea; N-phenyl-N-p-dimethylaminophenylurea; N-n-octadecyl- N p dimethylaminophenylurea; N-phenyl-N-p-aminophenylurea; N phenyl N p-dimethylaminophenylthiourea; N-phenyl-N-p-diethylaminophenylurea; N,N'-bis- (p dimethylaminophenyl)thiourea; N-p-hydroxyphenyl- N-(p-n-butylaminophenyl)urea; N-p-ethoxyphenyl-N-phydroxyphenylurea; N p ethoxyphenyl-N'-p-dimethylaminophenylurea; N-p-aminophenyl-N-p-hydroxyphenylurea; and N-p-isobutylaminophenyl-N-p-hydroxyphenylurea at concentrations described hereinbefore effective protection and stabilization are obtained.

We do not intend, however, that our invention be re stricted to such concentrations as in the specific examples cited above. Thus, the quantity of tetraethyllead stabilizer required is dependent both upon the concentration of the tetracthyllead and the degree of instability of the fuel carrier. However, in general, we can employ between about 0.1 and 15 milligrams per 100 milliliters of tetraethyllead-hydrocarbon solution. When the stabilizers of the present invention are employed directly in organolead antiknock agents, such as, for example, tetraethyllead, or in organolead antiknock fluids, comprising, for example, tetraethyllead and chlorine and bromine corrective agents or scavengers, we can employ somewhat: larger quantities of our stabilizers. For example, in such compositions we prefer to employ between about 0.1 and 20 parts of hydroxyand amino-substituted phenyl ureas and thioureas per parts of contained tetraethyllead, Thus our stabilizers of organolead antiknock additives, organolead antiknock fluids and fuel containing such material can be satisfactorily employed in a wide range of concentrations, and we do not intend that our invention be restricted to the specific quantities mentioned herein. Furthermore, we can successfully employ the stabilizers of the present invention in antiknock fluids containing diverse organic halogen materials commonly termed scavengers. Thus, we can utilize our stabilizers in antiknock fluids containing organic halogen compounds, such as, for example, those disclosed in U. S. 1,592,954; 1,668,022; 2,364,921; 2,398,281; 2,479,900; 2,479,901; 2,479,902; 2,479,903; and 2,496,983. Likewise, additional materials can be present in the stabilized organolead antiknock fluids of the instant invention. Thus, the hydroxyand amino-substituted phenyl ureas and thioureas can be successfully employed in antiknock mixtures containing diverse organic dyes, phosphorus-containing materials or other metal organic compounds in addition to organolead antiknock agents. Moreover, the stabilizers of the present invention can be utilized for the protection of the so-called mixed alkyl lead antiknock agents such as, for example, mixtures of the various methyl-ethyl-lead antiknocks, such as, methyltriethyl-, dimethyldiethyl-, and trimethylethyllead as well as tetramethyllead itself.

In resume, our invention resides in providing new compositions stable to oxidation comprising organolead antiknock agents or material such as, for example, antiknock flunds and fuel for internal combustion engines containing organolead antiknock agents and a member of the group consisting of ureas and thioureas wherein at least one of the nitrogen atoms is substituted with a radical selected from the group consisting of hydroxyphenyl, aminophenyl, and alkylaminophenyl, and the other nitrogen atom is substituted with a radical selected from the group consisting of alkyl, cycloalkyl and aryl. It is to be understood that organolead antiknock agents per se are normally susceptible to some deterioration in the presence of oxygen, particularly during blending, storage and handling operations. Likewise, materials containing organolead antiknock agents, such as antiknock fluids of the character described hereinbefore and frequently internal combustion engine fuel, particularly petroleum hydrocarbon fuel having a relatively high olefinic content, are normally susceptible to such deterioration. Despite the fact that certain fuels for internal combustion engines are relatively stable, the blending therein of an organolead antiknock agent or fluid produces a fuel composition normally tending to deteriorate in the presence of oxygen. Therefore, the effectiveness of the stabilizers of the present invention in obviating such deleterious deterioration in the presence of oxygen or ozone of organolead materials per se and compositions containing such materials constitutes an important advancement in the art.

We have disclosed a number of preferred embodiments of our invention and illustrated several means whereby protection can be afforded to tetraethyllead and organic materials sensitive to attack by oxygen containing tetraethyllead. Our invention is not intended to be limited to the specific embodiments of our invention herein or to the means described herein for obtaining the advantages possible in employing our compounds, as other methods of practicing our invention will be apparent to those skilled in the art. This application is a continuation-in-part of our prior co-pending application, Serial No. 200,115,

filed December 9, 1950, now U. S. Patent 2,683,081,

7 granted July 6, 1954.

wherein R1 is selected from the group consisting of alkyl, cycloalkyl, aryl and substituted aryl, said substituted aryl containing a radical selected from the group consisting of hydroxy, amino and alkylamino, R3 and R4 are selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, aralkyl and alkaryl, A is selected from the group consisting of hydroxy, amino and hydrocarbon derivatives thereof, and X is selected from the group consisting of oxygen and sulfur.

2. A new composition consisting essentially of an alkyllead antiknock additive, lead scavenger material, and, in an amount that stabilizes the additive against premature deterioration, a material having the general formula R1NHG-N' wherein R1 is selected from the group consisting of alkyl, cycloalkyl, aryl and substituted aryl, said substituted aryl containing a radical selected from the group consisting of hydroxy, amino and alkylamino, R3 and R4 are selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, aralkyl and alkaryl, A is selected from the group consisting of hydroxy, amino and hydrocarbon derivatives thereof, and X is selected from the group consisting of oxygen and sulfur.

3. A new composition consisting essentially ofa nonolefinic petroleum hydrocarbon motor fuel for internal combustion engines, and an alkyllead anti-knock agent, and, in an amount sufficient to prevent premature decomposition of the alkyllead, a material having the general formula wherein R1 is selected from the group consisting of alkyl, cycloalkyl, aryl and substituted aryl, said substituted aryl containing a radical selected from the group consisting of hydroxy,.amino andalkylamino, R3 and R4 are selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, aralkyl and alkaryl, A is selected from the group consisting of hydroxy, amino and hydrocarbon derivatives thereof, and X is selected from the group consisting of oxygen and sulfur.

4. The composition of claim 1 wherein said material is N'-(p-hydroxyphenyl)-N-phenyl-urea.

5. The composition of claim 1 wherein said material is N-phenyl-N'-(p-hydroxyphenyl) thiourea.

6. The composition of claim 3 wherein said material is present in amount between about 0.1 and 15 milligrams per 100 milliliters of said fuel composition.

7. The composition of claim 6 wherein said material is N'-(p-hydroxyphenyl)-N-phenyl-urea.

8. The composition of claim 6 wherein said material is N-phenyl-N'-(p-hydroxyphenyl) thiourea.

References Cited in the file of this patent UNITED STATES PATENTS 2,154,341 Martin Apr. 11, 1939 2,199,828 Bogdan May 7, 1940 2,373,049 Pedersen Apr. 3, 1945 2,407,261 Downing Sept. 10, 1946 2,477,872 Haury Aug. 2, 1949 2,683,081 Hill et al. July 6, 1954 it t: 

3. A NEW COMPOSITION CONSISTING ESSENTIALLY OF A NONOLEFINIC PETROLEUM HYDROCARBON MOTOR FUEL FOR INTERNAL COMBUSION ENGINES, AND AN ALKYLLEAD ANTI-KNOCK AGENT, AND, IN AN AMOUNT SUFFICIENT TO PREVENT PREMATURE DECOMPOSITION OF THE ALKYLLEAD, A MATERIAL HAVING THE GENERAL FORMULA 